The cytokine MIF controls daily rhythms of symbiont nutrition in an animal–bacterial association
Eric J. Koch, Clotilde Bongrand, Brittany D. Bennett, Susannah Lawhorn, Silvia Moriano‐Gutierrez, Marko Pende, Karim Vadiwala, Hans‐Ulrich Dodt, Florian Raible, William E. Goldman, Edward G. Ruby, Margaret McFall‐Ngai
Abstract
MIF (EsMIF) in the light-organ transcriptome, led us to ask whether EsMIF might be the gatekeeper controlling the periodic movement of the hemocytes. Western blots, ELISAs, and confocal immunocytochemistry showed EsMIF was at highest abundance in the light organ. Its concentration there was lowest at night, when hemocytes entered the crypts. EsMIF inhibited migration of isolated hemocytes, whereas exported bacterial products, including peptidoglycan derivatives and secreted chitin catabolites, induced migration. These results provide evidence that the nocturnal decrease in EsMIF concentration permits the hemocytes to be drawn into the crypts, delivering chitin. This nutritional function for a cytokine offers the basis for the diurnal rhythms underlying a dynamic symbiotic conversation.